Mechanism of Al on FeCrAl steam oxidation behavior and molecular dynamics simulations

Abstract

FeCrAl alloys exhibit excellent oxidation resistance in high temperature steam environment for the Al percent in the alloy. However, the Fe–Cr–Al alloy becomes more brittle and the defects generated after irradiation also increase with the increasing Al content. To address this obstacle and elucidate the mechanism for the impact of Al on FeCrAl oxidation behavior, in this study, oxidation experiments and molecular dynamics simulations were used to investigate the oxidation of the Fe–Cr–Al alloy in high temperature steam environment with different contents of Al (2 wt% (weight percent) ∼ 6 wt%). When the Al content is between 2 wt% and 3 wt%, the Fe–Cr–Al alloy will form the thick and porous FeCr2O4 film with Fe2O3, Cr2O3 and Al2O3 in it, when the Al content is between 4 wt% and 6 wt%, the Fe–Cr–Al alloy can form a continuous Al2O3 film observed with SEM. From molecular dynamics simulation, it also found that Al2O3 continuous film is easier to form with increasing Al content. The oxidation thermodynamic analysis indicated that Al activity becomes higher in the alloy matrix with increasing Al, and Al can induce reduction reaction with Cr2O3, Fe2O3 and FeCr2O4 in the high temperature steam environment.